Question

我不敢肯定我目前的执行情况:

function isNodeList(nodes) {
    var result = Object.prototype.toString.call(nodes);
    // modern browser such as IE9 / firefox / chrome etc.
    if (result ===  [object HTMLCollection]  || result ===  [object NodeList] ) {
        return true;
    }
    //ie 6/7/8
    if (typeof(nodes) !=  object ) {
        return false;
    }
    // detect length and item 
    if (!( length  in nodes) || !( item  in nodes)) {
        return false;
    }
    // use the trick NodeList(index),all browsers support
    try {
        if (nodes(0) === null || (nodes(0) && nodes(0).tagName)) return true;
    }
    catch (e) {
        return false;
    }
    return false;
}

A common situation is {length:1,item:function(){return [];}}
The value of result in chrome / safari / opera is [object NodeList] .
In firefox and IE 9 , it is [object HTMLCollection] .

标准价值是什么?

Answer 1

如下:

NodeList.prototype.isPrototypeOf(nodes)

@DavidSpector, for HTMLCollection you can similarly use :

HTMLCollection.prototype.isPrototypeOf(collection)

Answer 2

I would structure the code differently:

function isNodeList(nodes) {
    var stringRepr = Object.prototype.toString.call(nodes);

    return typeof nodes ===  object  &&
        /^[object (HTMLCollection|NodeList|Object)]$/.test(stringRepr) &&
        (typeof nodes.length ===  number ) &&
        (nodes.length === 0 || (typeof nodes[0] === "object" && nodes[0].nodeType > 0));
}

注:

less return paths make easier-to-read code
stick with one type of logic, if possible (i.e. use less negated checks)
"item" is not mandatorily in a nodeList
use hasOwnProperty() instead of in
use square brackets to index into the list
I don t think a try/catch is really necessary, but that might be wrong - you decide
check for nodeType instead of tagName, as text nodes or comments do not have a name
add more checks to the && chain if you see fit

Answer 3

在这里,如果物体在现代浏览器中是无能为力的,如何检验:

if (nodes instanceof NodeList) {
  // It s a NodeList object
}

Answer 4

<>>>>:

Element.prototype.isNodeList = function() {return false;}
NodeList.prototype.isNodeList = HTMLCollection.prototype.isNodeList = function(){return true;}

use like this:

var d; // HTMLCollection|NodeList|Element
if(d.isNodeList()){
  /*
    it is HTMLCollection or NodeList
    write your code here
  */
}else{
  /*
    it is not HTMLCollection and NodeList
    write your code here
  */
}

Answer 5

如果变数是超额收集,或是单质元素

  var foo = document.getElementById( mydiv );
  var foo2 = document.getElementsByClassName( divCollection );
  console.log(foo instanceof HTMLElement);
  console.log(foo instanceof HTMLCollection);

Answer 6

答案可能真的晚了,但......。

if (nodes ==  [object NodeList] ) {
  // It s a nodeList
}

Answer 7

我制定了所有答案的基准,以便看到,最快的是批准。排在<代码>NodeList.prototype.isPrototypeOf(nodes)上,迄今为止是最快的。但在正常使用情况下,<代码>诺德列斯/代码>也应予罚款。

我个人不会选择<代码>s NodeList的功能,因为其缓慢、习俗和太多的间接费用。

Answer 8

下面是 Java本功能,以检查在OMM有一个网页上是否存在超声波或无声波,以下代码在上测试。 Chrome Dev Technologies > Console tab of https://stack Exchange.com/:

function ifElemExists(elem) {
    if((elem instanceof NodeList) || (elem instanceof HTMLCollection)) return true;

    return false;
}

const elem1 = document.querySelector( .blah );
const elem2 = document.querySelectorAll( .siteHeader );
const elem3 = document.getElementById( footer );
const elem4 = document.getElementsByClassName( blah );

console.log(ifElemExists(elem1)); // Output: false
console.log(ifElemExists(elem2)); // Output: true
console.log(ifElemExists(elem3)); // Output: false
console.log(ifElemExists(elem4)); // Output: true

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